[Mod Support] Mars/Duna Direct

[bigyihsuan]

Support for the Duna Direct mod.

I've placed the parts in tier 9 for the following two reasons:

• The original Mars Direct proposal is from 1990, way post-Apollo.
• The proposal calls for a Shuttle-derived rocket, similar to SLS.

Currently the engines use kerolox, when I figure it out they'll use metholox instead.